M'Baya B, Fegueur M, Servouse M, Karst F
Laboratoire de Biochimie et Genetique des Microorganismes, Universite de Poitiers, France.
Lipids. 1989 Dec;24(12):1020-3. doi: 10.1007/BF02544072.
Squalene synthetase (EC 2.5.1.21) and squalene epoxidase (EC 1.14 99.7) activities have been measured in cell-free extracts of wild type yeast grown in aerobic and semi-anaerobic conditions as well as in sterol-auxotrophic mutant strains grown aerobically. The results show that both enzymes are induced resulting in an almost two- to five-fold increase in enzymatic activities in mutant strains containing limited sterol amounts and are repressed in the wild type strain cultured in anaerobiosis in excess of sterol. The results show also that squalene epoxidase is repressed by lanosterol, and that the mevalonic acid pool may regulate squalene synthetase levels. The large change in the activities of the two enzymes, depending on the sterol needs of the cells, as well as their low specific activities in comparison with those of the enzymes involved in the early stages of sterol synthesis strongly suggests that squalene synthetase and squalene epoxidase are of importance in regulating the amount of sterol synthesized by yeast.
在需氧和半厌氧条件下生长的野生型酵母以及需氧生长的甾醇营养缺陷型突变菌株的无细胞提取物中，已测定了角鲨烯合成酶（EC 2.5.1.21）和角鲨烯环氧化酶（EC 1.14 99.7）的活性。结果表明，这两种酶在含有有限甾醇量的突变菌株中均被诱导，导致酶活性几乎增加了两到五倍，而在厌氧培养且甾醇过量的野生型菌株中则受到抑制。结果还表明，羊毛甾醇可抑制角鲨烯环氧化酶，并且甲羟戊酸池可能调节角鲨烯合成酶的水平。这两种酶的活性变化很大，取决于细胞对甾醇的需求，并且与甾醇合成早期阶段所涉及的酶相比，它们的比活性较低，这强烈表明角鲨烯合成酶和角鲨烯环氧化酶在调节酵母合成甾醇的量方面具有重要作用。
